removing rust on molds..

[Mandolin man]

I was given three Lyman molds that have a pretty good coat of rust.. There seems to be no pitting.. What can I do to get them back in usable shape..

[Gray Fox]

Put the mold blocks in a container with high test Coke and let sit for a day or two. Rinse in very hot water and they should be OK. Fifty years ago I learned this from Vietnamese who did this to their bicycle chains. GF

[Walks]

Home Depot sells Rust Remover in a gallon jug. It's usually by the WD-40.
I've used it on rusty molds off flea-bay.

Disassemble the molds, put them in a small plastic bucket. Cover with rust remover, put cover on bucket, old piece of plywood , plexiglass, old dinner plate.
Leave in for 2-3 hours (read directions) remove, rinse & brush hard with bronze brush.
If clean, dry it and oil all screw threads. Put it to work or oil it and put it to work. I use canned air to blow out the screw holes.
Works for me.

[ericandelaine1975]

You can use naval jelly. They have it at any auto parts store. Just read the instructions on the bottle or if there is someone in your area that has a soda blaster. Soda blasting won't hurt it at all. Its just baking soda.

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[lightman]

I've used EvapoRust on dies and other tools with good results. Just beware that it also removes blueing.

[toallmy]

I have cleaned up a cruddy RCBS 358-150 KT mold with citrus acid and a toothbrush with like new results , but in white when finished , no blacking left at all . But a good dip in the casting pot fixed that after a good preheating . A light lapping of the cavities by hand with toothpaste makes it a pleasure to cast with .

[toallmy]

If the cavities are clear of rust you may want to just preheat the molds and cast some boolits with them .

[rwadley]

Evaporust is amazing

[ryan28]

Another Evaporust convert here too.

[John Boy]

Coat the molds with a brushing of 50:50 mix of ATF & Acetone. About an hour will do - brush mold with a bronzr or brass brush - Wipe clean

[dragon813gt]

I've used EvapoRust on dies and other tools with good results. Just beware that it also removes blueing.

That’s because bluing is rust. Evaporust is what you want to use. It not only removes the rust it neutralizes is so it doesn’t spread. Depending on the rust you may get some dark discoloring. But for a mold this shouldn’t be an issue. It’s practically magic in a bottle.

[Bohica793]

Evaporust. 'Nuff said.

[MrWolf]

Another Evaporust +

[EDG]

Common rust remover is phosphoric acid in a solution with water.
Coca Cola contains a solution of phosphoric acid.

Nitric acid will also remove rust but

20% Nitric acid is used in industry all across the country to clean and passivate stainless steel. Stainless steel will stain and corrode if it has particles from carbon steel embedded in the material. The steel particles come from chains, fork lift forks, other materials in storage racks and from saws presses and other metal working tools.
20% nitric acid dissolves these rust stans and steel particles.
But it will also dissolve your entire part if left too long.
Typically the surface oxide goes then the part bubbles and turns black. Hydrogen gas bubbles off of the part and given several hours to overnight your carbon steel will disappear.
The high chromium and nickel content of stainless steel leaves it untouched.

[squidtamer]

Another Evaporust convert here too.

Yup here too. Can't believe you can get it at Harbor Freight... LOL

Now I'll second a few of the other ideas. Citric Acid or Lemishine or even some slightly watered down Coke. Gotta test things though, see how much material it takes off.

DON'T use Naval Jelly on the dies without testing it first! tends to be a bit.. aggressive, sometimes.